Much to Savor, and Worry About, Amid Mild Winter’s Early Blooms

Scenes more like spring, including a Japanese flowering apricot tree, arrived early at the New York Botanical Garden.Credit
Suzanne DeChillo/The New York Times

At the New York Botanical Garden in the Bronx, an experimental plot was in full flower on a recent February afternoon, as the thermometer edged toward 60.

The Japanese camellias, which typically bloom in early spring, have displayed their rose-hued flowers continuously since December. Honeybees, a rarity before late March, were nursing the tiny pink clusters on a Dawn viburnum, while the Adonis amurensis, a ground-hugging spring ephemeral, was a profusion of yellow.

“This is the earliest I’ve seen all of these things in flower,” said Todd Forrest, the garden’s vice president for horticulture and living collections. “The ground isn’t even frozen. That’s shocking.”

The horticulturalists in the Bronx call it the global-warming garden, and in a winter notable for its consistent mildness, it is hardly unusual. From the Shakespeare Garden in Central Park to the Chicago Botanic Garden, flowering bulbs and other plants are bursting out two to four weeks ahead of schedule. Snowdrops are up; daffodils, crocuses and hellebores are already in flower; trailing phlox has opened; and, farther afield, even magnolia trees are starting to bloom on the National Mall in Washington.

Complaining about balmy winter days and an early display of color might seem churlish, but the early run of warm weather is not without its downside.

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A bee, a rarity before late March, gathers nectar from an Adonis amurensis at the New York Botanical Garden.Credit
Suzanne DeChillo/The New York Times

For one thing, if there is a cold snap, plants and trees are vulnerable to damaged blossoms and, potentially, a falloff in seed production. With the ground still soft in many places and no snow cover, squirrels — already suffering from the acorn shortage last fall — have been digging up bulbs. Populations of insect pests, normally kept in check by freezing temperatures, are expected to grow this year.

And when spring finally does arrive a month from now — according to the calendar anyway — the show might be ho-hum. “You’ll see a long, gradual kind of spring,” said Maria Hernandez, director of horticulture for the Central Park Conservancy. “But it won’t be the pizazz that we had last spring.”

It is hard to draw conclusions about the pace of warming from a single winter, and indeed, the last decade in New York City has been one of the snowiest on record. Still, Fred Gadomski, a meteorologist at Pennsylvania State University, said that temperatures were above normal in 80 percent of the days in the past three months in the city. Strong winds from the Pacific Ocean have blanketed most of the country with unusually mild air.

“That’s the distinguishing item this winter — the consistency of the mildness,” Mr. Gadomski said. “If you took away that week in mid-January where it really was sort of cold, it would be the year without a winter.”

Coincidentally, the federal Agriculture Department last month issued a new national map showing plant hardiness zones, which start with the coldest regions in the north and work their way south. In its first update since 1990, the map showed clear signs of things’ heating up. New York City, for instance, moved into a warmer zone, going from a “warm 6” to a “cold 7,” as Mr. Forrest put it.

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Todd Forrest, vice president for horticulture at the New York Botanical Garden, smells a Dawn viburnum, which normally blooms in March.Credit
Suzanne DeChillo/The New York Times

David W. Wolfe, a professor of plant and soil ecology at Cornell University and an expert on climate change, said the temperatures this winter appeared to “represent an extreme,” even within the context of climate change. But, he said, the federal climate-zone guides from 1960, 1990 and this year reveal “an extremely fast pace” of change.

“This winter, when they do the final analysis, will be close to an all-time record breaker,” Dr. Wolfe said. “It’s a rare event. But I think it will become less rare.”

That is little solace to farmers, horticulturalists and home gardeners, who have worried about their charges this winter. Rod Dressel Sr., who owns a 300-acre apple orchard in the Hudson Valley, said the buds on his trees were starting to swell. If the trees flower too early, a freeze could kill the blossoms and, with them, the promise of apples this fall.

“I’m looking at 52 degrees here,” he said. “We’re concerned the tree will think it’s spring way too early. History has shown that we’re vulnerable to frost damage right up into the middle of May.”

In parks and public gardens across the country, visitors and horticulturalists alike are marveling at the winter blooms and rooting for their survival.

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Snowdrops, seen in Central Park, should be able to withstand a sudden change in temperature.Credit
Suzanne DeChillo/The New York Times

What happens to a luscious pink magnolia blossom if temperatures plunge? “It just turns brown and ugly,” said Holly H. Shimizu, the executive director of the United States Botanic Garden in Washington.

She wishes she could tell the plants to slow down. “The buds are swelling on the shadblow trees and I want to say, ‘Hold on, don’t do it,’ ” she said. “If it gets cold fast, they could be damaged and won’t bloom again.”

One concern with premature flowers is pollination. While honeybees were in evidence at the New York Botanical Garden, there were fewer at the United States Botanic Garden. “When plants get in this off-kilter blooming, sometimes it doesn’t coincide with the life cycle of the pollinator,” Ms. Shimizu said. “If pollination doesn’t occur, then we don’t get the fruit production.”

Some visitors to public gardens have felt conflicted by the unexpected splashes of pink and yellow. Dennis Mardon, a high school math teacher in the Bronx, was relieved to find that the daffodil shoots had yet to burst at the New York Botanical Garden, especially after seeing a couple of dozen in bloom on the nearby Mosholu Parkway.

“On the one hand, it’s great to see flowers this early — it lifts your spirits,” said Mr. Mardon, a Bronx native and lifelong gardener. “On the other hand, it creates apprehension. Gardens need an opportunity to rest, and that’s what a good winter provides.”

Should the weather take a sudden turn, daffodils, crocuses and snowdrops should be able to withstand any freezing temperatures, even snow. Not so the Japanese apricots in the Ladies’ Border, the experimental plot at the botanical garden, which was redesigned in 2002 with plants that do well in places like North Carolina or Virginia, one or two hardiness zones south of New York.

The experimental garden could, over time, serve as a blueprint for a new world of horticulture. “This is not normal,” said Mr. Forrest, touring the garden in only a suit and tie and no overcoat. “If this becomes the new normal, then we have to change the way we think about the plants we use and how we protect them.”

A version of this article appears in print on February 27, 2012, on page A13 of the New York edition with the headline: Much to Savor, and Worry About, Amid Mild Winter’s Early Blooms. Order Reprints|Today's Paper|Subscribe